[FFmpeg-devel] Patch question

[Moritz Barsnick]

Hi Mats,

On Tue, Dec 15, 2015 at 16:58:41 +0100, Mats Peterson wrote:
> Sorry if this may sound idiotic, but if I provide a unified patch for a 
> file that is newer/different from the one I have here, it won't work, right?

"It depends." ;-)

By the way, git handles this kind of stuff nicely.

It may or may not work. Obviously, if the file hasn't changed upstream,
your patch will still apply.

a) Best case: The files haven't changed upstream, your diff still
   applies.
b) Good case: Upstream changed only unrelated parts of those file, your
   diff applies, perhaps with an offset (i.e. shifted in line numbers).
b2) Almost as good: The unrelated changes are close to your changes, so
   you get a so-called fuzz.
c) Bad case: Related parts were changed. Your diff won't apply, you
   have to reintegrate your changes, perhaps even differently.
d) Worse case: Your patch applies, but affected methods were
   incompatibly changed. This leads to build or runtime errors, or
   broken functionality.

It's always a good idea to check upstream changes to see whether they
affect your patch. Most likely, a) or b) applies, but you don't know
until you've checked. :-)

Moritz